1. Field of the Invention
The present invention relates to a fluid machine for converting fluid energy to mechanical energy or vice versa, such as a compressor for compressing a gas.
2. Description of the Related Art
Regarding this type of fluid machine, a compressor suitable for use for a vehicular air-conditioning system configured, as described below, is known.
Specifically, a crank chamber is defined in a housing, and a drive shaft is rotatably supported by the housing across the crank chamber thereof. In the crank chamber, a swash plate acting as a cam plate is supported on the drive shaft via a rotatable support member to be able to rotate in synchronism with the drive shaft and be inclined with respect to a plane vertical to the axis of the drive shaft. A plurality of pistons are coupled to the outer peripheral portion of the swash plate. A cylinder block constituting a part of the housing is formed with a plurality of cylinder bores, at predetermined spatial intervals, at positions surrounding the drive shaft. The head of each piston is inserted into the corresponding one of the cylinder bores to be able to move reciprocally therein.
When the drive shaft is driven to be rotated by the driving force transmitted thereto, via a belt or the like, from an external drive source such as a vehicle engine, the swash plate is rotated via the rotatable support member synchronously with the drive shaft, and the rotational movement of the swash plate is converted to the reciprocal movement of the pistons. Thus, a compression cycle, including the suction of a refrigerant gas into the cylinder bores, the compression of the refrigerant gas and the discharge of the compressed refrigerant gas from the cylinder bores, is repeated.
A compressor having a mechanism for changing a displacement as described below is also known.
Specifically, a discharge chamber, in which the compressed refrigerant gas stays temporarily, and the crank chamber are in fluid communication with each other through a gas feed passageway having a control valve. The control valve has the function of adjustably changing the opening area of the gas feed passageway and thereby adjusting the amount of the refrigerant gas at high pressure supplied into the crank chamber from the discharge chamber. By adjusting the feeding amount of the refrigerant gas in discharge pressure in this way, the pressure in the crank chamber is changed, so that the difference between the pressure in the crank chamber exerted on one side of the piston and the pressure in the cylinder bore exerted on the other side of the piston is changed. Along with this change of the difference in the pressure, the inclination angle of the swash plate with respect to a plane vertical to the axis of the drive shaft is adjustably changed thereby to adjust the piston stroke, i.e. the amount of displacement.
The compressor described above comprises many sliding portions such as bearings of the drive shaft, the outer surface of each piston and the inner surface of the corresponding cylinder bore, and the coupling between the swash plate and each piston. In the case where foreign matter is caught in any of these sliding portions, the smooth movement of the particular sliding portion is adversely affected, often resulting in an increased load on the external drive source. Especially, seizing on the sliding portion has a serious effect on the external drive source.
Further, in the compressor described above having the mechanism for changing the displacement, foreign matter intruding into the control valve may be caught in the space between a valve body and a valve hole of the control valve so that it may impair the function of adjusting the opening degree of the opening area thereof. Once the function of adjusting the opening degree of the control valve is impaired in this way, the supply of the refrigerant gas in discharge pressure into the crank chamber fails to be adjusted properly, thereby considerably reducing the accuracy of the adjusted displacement.
Another known compressor includes a filter at the inlet of the refrigerant gas into the compressor from an external refrigerant circuit, at the inlet of the gas feed passageway, or at the other locations, in order to avoid troubles which might be caused by the intrusion of foreign matter.
A mounting configuration for one of these filters, which is mounted at the inlet of the gas feed passageway, for example, is illustrated in FIG. 7.
Specifically, a mounting recess 103 is formed on an inner bottom surface of a discharge chamber 102 defined in an outer peripheral portion of a rear housing 101, and an inlet to the gas feed passageway 104 opens into the mounting recess 103. An inner peripheral surface of the mounting recess 103 is formed with a step 105 at the substantially central portion thereof and an annular groove 106 positioned between the opening and the step 105 of the mounting recess 103. A filter 107 in the form of a circular disk, for example, made of a woven wire, rests on the step 105 and is securely retained there by a snap ring 108 mounted in the annular groove 106.
with the conventional configuration described above, when mounting the filter 107 at the inlet to the gas feed passageway, at first, it should be dropped onto the step 105 in the mounting recess 103. Then, after setting the snap ring 108 into registry with the opening of the mounting recess 103 while reducing the diameter thereof by means of pliers or the like, the snap ring should be released from the force of reducing the diameter thereof and thus fitted into the annular groove 106. Mounting the filter 107 in this way requires skilled work which is difficult to automate and which has to be inevitably performed manually, thereby leading to the problem of a high manufacturing cost for the compressor.
The compressor, whose drive source is the vehicle engine, is generally mounted in the vicinity of the vehicle engine in the engine compartment. Since the space available for arranging the compressor in the engine compartment is limited the demand for a smaller compressor is increasing. A smaller compressor also reduces the size of the opening of the discharge chamber 102 formed with the mounting recess 103. A space is also required to screw a through bolt for securely coupling the housing of the whole compressor on the outer peripheral portion of the rear housing 101. This space forms a protruding portion on the inner peripheral surface of the discharge chamber 102.
On the other hand, a required filtration area sufficient for a predetermined filtering capacity must be maintained. It is therefore difficult to reduce the radial size of the filter 107. The resulting problem is that the location for the filter 107 to be arranged in the rear housing 101 is severely restricted.
An idea for reducing the radial size of the filter 107 while maintaining a required filtration area is to convexly protrude a portion of the filter 107 along the axis thereof. Protrusion of the filter 107 toward the opening of the mounting recess 103, however, makes extremely difficult the work of mounting the snap ring 108. On the other hand, if the filter 107 is protruded toward the bottom of the mounting recess 103, a new problem arises in that foreign matter is liable to accumulate in the protrusion of the filter 107.
The present invention has been developed in order to solve the above-mentioned problems of the prior art and it is an object thereof to provide a fluid machine in which the step of mounting the filter on the flow passageway can be easily automated with an improved latitude of filter arrangement.
In order to achieve the object described above, according to a first aspect of the invention, there is provided a fluid machine which includes a housing assembly provided with a plurality of pressure chambers, a plurality of working chambers for changing a pressure of a fluid accommodating therein to a predetermined level, and a plurality of communication passageways for providing fluid communication between an external fluid circuit and the pressure chambers or between the pressure chambers, wherein the fluid machine further includes a filter arranged in an opening end of one of the communication passageways and provided with means for securing the filter in the opening end by press fitting or caulking.
In this fluid machine, the filter can be fixedly secured to the housing assembly by the simple work of placing the filter in position corresponding to the opening end of the housing assembly and press fitting the filter directly in the opening end or by the simple work of inserting the filter and then pressing the exposed portion thereof against the housing assembly. Thus, the step of mounting the filter can be easily automated.
In one preferred embodiment of the above-mentioned fluid machine, the filter is arranged in the opening end defined as an inlet to the communication passageway in the direction of the fluid flow.
In this fluid machine, in addition to the advantage described above, the intrusion of foreign matter into the communication passageway can be effectively suppressed. Further, since the filter is pressed against the communication passageway under the pressure of the fluid, the filter is prevented from easily moving out of position.
In another preferred embodiment of the above-mentioned fluid machine, the filter includes a filter member in a three-dimensional shape.
In this fluid machine, in addition to the advantages described above, the filter can be reduced in radial size while maintaining a required filtration area, thereby improving the latitude in the design of the communication passageway.
Further, preferably, at least a portion of the filter member is formed to project from the opening end formed in the housing assembly.
In this fluid machine, in addition to the advantage described above, the filter member can be structured to prevent foreign matter from being accumulated therein, thereby to improve a filter durability.
In a further preferred embodiment of the above-mentioned fluid machine, the fluid machine comprises a compressor for compressing a compressive fluid and the pressure chambers include a suction chamber for accommodating the compressive fluid supplied from the external fluid circuit and a discharge chamber for accommodating the compressive fluid discharged from the working chamber. Preferably, a recess is formed on the inner surface of the discharge chamber and the filter is secured in the recess by press fitting or caulking. More preferably, a part of the filter projects beyond the inner surface of the discharged chamber.
With a compressor for compressing a compressive fluid, i.e. a gas, a sufficient amount of liquid is not always in contact with the sliding surfaces thereof but only a small amount of lubricant is supplied. For this reason, foreign matter attached to the sliding surfaces is sometimes difficult to wash off. In this fluid machine according to preferred embodiment, the bad influence of foreign matter on the fluid machine can be reduced and the advantage described above can be conspicuously exhibited.
Preferably, in the above-mentioned preferred embodiment, at least one of the communication passageway is/are provided with a control valve for adjustably changing the opening area of the communication passageway. More preferably, the filter is arranged at the inlet to the communication passageway provided with the control valve.
This fluid machine has the advantage, in addition to one described above, that the adverse effect that foreign matter may have on the smooth change of the opening area of the communication passage can be prevented.
More preferably, the pressure chambers include a crank chamber, in which a pressure of the compressive fluid accommodated therein is changed by the operation of the control valve and across which a drive shaft is provided, said crank chamber accommodating a cam plate inclinably mounted on the drive shaft, and wherein the working chamber accommodates a piston coupled to the cam plate to be able to move reciprocally therein, whereby the inclination angle of the cam plate with respect to a plane vertical to the axis of the drive shaft, is changed due to the change of difference between the pressure in the crank chamber exerted on one side of the piston and the pressure in the working chamber exerted on the other side of the piston caused by changing the pressure in said crank chamber, thereby to adjustably change the displacement of the fluid machine.
This fluid machine has, in addition to the advantage described above, the advantage that intrusion of foreign matter into the control valve is prevented thereby to ensure the accurate operation of the control valve. As a result, the accurate operation of changing the displacement of the fluid machine can be ensured.
In a further preferred embodiment of the above-mentioned fluid machine, the drive shaft is kept connected to an external drive source.
With the compressor of a clutchless type, as described above, once a malfunction of the control valve occurs, the fluid machine may continue to run while the controllability of the displacement is considerably reduced. In such a situation, the fluid machine may operate with an operating displacement not coincident with the required displacement. For this reason, the advantage of the fluid machine is exhibited especially conspicuously by a compressor of a clutchless type.
In one preferred embodiment, the means for securing the filter comprises a ring arranged at a periphery of the filter.
Preferably, the ring of the filter may have a diameter slightly larger than that of the opening end and the filter may be fixedly secured in the opening end by press fitting.
Also, preferably, the ring may have substantially the same diameter as that of the opening end and be deformed plastically by caulking to engage with a groove formed in the opening end. More preferably, the ring is made of plastically deformably material selected from a group including resin, aluminum, lead and copper.
Also, preferably, the ring has a first elastically deformable engaging means on its periphery, and a second engaging means is provided on the opening end, the second engaging means adapted to engage the first engaging means.
According to a second aspect of the invention, there is provided a fluid machine which includes a housing assembly provided with a plurality of pressure chambers, a plurality of working chambers for changing a pressure of a fluid accommodating therein to a predetermined level, and a plurality of communication passageways for providing fluid communication between an external fluid circuit and the pressure chambers or between the pressure chambers, wherein the fluid machine further includes: a filter arranged in an opening end of one of the communication passageways; and, a securing element to secure the filter in the opening end by the application of a mechanical force to the securing element.
Preferably, the securing element comprises a ring arranged at a periphery of the filter.
Also, preferably, the application of the mechanical force is achieved by press fitting or caulking.